1. Field of the Invention
This invention relates to the art of bonding between ceramics and metals.
2. Description of the Prior Art
Broadly, known methods of bonding ceramics and metals together include (1) an adhesive method, (2) a metallizing method and (3) a spray coating method. However, these methods have the following drawbacks.
(1) The adhesive method is the simplest method but adhesion strength at high temperatures is low.
(2) The metallizing method is a method which comprises placing a powder of metal, such as, Mo, Mo--Mn or the like, on ceramics, heating the powder in a moistening atmosphere so as to metallize it on the ceramic, and after effecting Ni-plating on said metal, bonding the surface of said Ni-plating and said metal by soldering.
However, the drawback of this method is that, depending on the kind of ceramics used, it is difficult to carry out. Also, because a high heating temperature is required, considerable thermal stress is exerted on the ceramic upon cooling, thus causing an additional drawback by the ceramic's tendency to crack.
(3) The spray coating method is a method in which ceramic powder is fused and adhered to metals by spraying. The method is also disadvantageous in that the resulting bonding strength is low and the sprayed ceramic becomes porous.
As will be seen from the above, the prior art methods have such drawbacks that the bonding strength is not adequate, ceramics are liable to crack, and limitation is placed on the type of ceramic being applied.